For the longest time, since I first started playing tf2 when it came out, I really hated pyro. So much that I never played him, and never even kept any pyro weapons. I only have 20 or so hours as pyro and most of that was from dodgeball/prophunt back in the day.
Recently, though... I've been picking random to choose my class, and I don't mind lighting up some people with pyro from time to time, but I don't think I'll ever actually pick him on purpose.

Heavy, love the character and weapons, but the class feels... boring. No major mobility, no fancy meatshots, double jumps, rocket jumps, sticky jumps, stair stabs. He needs something to make him more interesting.

I've been playing TF2 for years now, and I still can't accomplish a thing as a Spy, apart from obviously rushing at enemy Sentry nests and hoping I'll maybe sap a building or two to death before the Engie inevitably shotguns me down. Anything else, like actual stealth? No, I'm completely clueless there.

While the classes I do like such as Spy or Medic are fairly viable
most of the time, classes I don't appreciate as much such as
Demo or Heavy I'm good enough to flatten most pubs with, and
become necessary plays when my team is lackluster. ._.